Packaging foil and process for producing same

ABSTRACT

Packaging foil comprising a flexible support foil, a top layer of a vinyl polymer, and an adhesion promoter or primer between the support foil and top layer, wherein the primer is a mixture of a chlorine or fluorine containing polymer, an organic compound of at least two isocyanate groups, and a reaction product having terminal hydroxyl groups and derived from a linear polyester with terminal hydroxyl groups and an organic diisocyanate.

11nited States Patent Ottmann et al.

[151 3,656,99 [4 1 Apr. 18, 1972 [54] PACKAGING FOIL AND PROCESS FORPRODUCING SAME [72] Inventors: Gerhard Ottmann; Clemens Lilienbeck,

both of Wuppertal-Barmen, Germany Dr. Kurt Herberts & Co., Vorm. OttoLouis Herberts, Berman, Germany [22] Filed: Feb. 25, 1970 [21] Appl.No.:14,237

[73] Assignee:

[30] Foreign Application Priority Data Feb. 26, 1969 Sweden ..2607/69[52] U8. Cl. ..1l7/75,99/171 LP, 117/76 F, 117/76 P, 117/138.8 E,ll7/l38.8 F,117/l38,8 N,

[51] Int. Cl. ..B32b 27/08, B44d H14 [58] Field of Search ..1 17/76 P,76 F, 75, DIG. 7; 161/l89,190, 184, 227, 231, 252

[5 6] References Cited UNITED STATES PATENTS 2,891,876 1/1959 Brownetal..117/75x 3,035,939 5/1962 Edwards ..l17/75 3,178,394 4/1965Christens0n.. ..161/l90 X 3,198,692 3/1965 Bridgeford.... 17/76 F X3,257,261 6/1966 Hochberg ..l6l/190 X 3,514,367 5/1970 James ..117/76 FX Primary Examiner-William D. Martin Assistant Examiner-Ralph HusackAtt0rney-Oberlin, Maky, Donnelly & Renner [57] ABSTRACT 18 Claims, NoDrawings PACKAGING FOIL AND PROCESS FOR PRODUCING SAME The presentinvention relates to a packaging or wrapping foil comprising a flexiblesupport foil, a top layer of a vinyl polymer and an adhesion promoterbetween the support foil and top layer, and constitutes an improvementover our prior, pending US. application, Ser. No. 765,040, filed Oct. 4,1968.

Packaging foils are known which consist of a support foil and a toplayer. According to the prior art, it is mainly foils of polyester,cellular glass or polypropylene which have so far been used as supportfoils. However, because these foils have an undesirable steam and gaspermeability, they are consequently provided with a coating which has apolyvinylidene chloride (PVDC) or polyvinyl chloride (PVC) base. ThePVDC or PVC coatings are produced by applying a dispersion or solutionof PVDC or PVC to the support foils and evaporating the solvent ordispersion agent. However, the PVDC and PVC coatings produced in thisway have an insufficient bonding with the support foils which are basedon synthetic plastics materials. Consequently, it has been proposed touse so-called adhesion promoters. Solutions or dispersions of theseadhesion promoters are applied to the support foil and the solventcontained therein is evaporated. Thereafter, the top layer, based onPVDC or PVC, is applied in the manner described above. Known adhesionpromoters (primers) include solutions or dispersions which are based onpolymeric alkylene imines (see German Auslegeschrift No. 1204559),polyamides, acrylates, isocyanates in combination with polyesters and/orpolyethers, and epoxy compounds in combination with amines andpolyamines.

These known packaging or wrapping foils have the disadvantage that thereis an insufficient adhesion between the top layer and support foil. Thisbecomes particularly apparent when these foils are kept for a relativelylong time under conditions similar to tropical conditions. Theinsufficient adhesion results in the foils losing the desirableimpermeability to steam and gas and being liable to be easily damaged.Since foils are widely used for packaging, for example, foods, for longperiods, any damage to the foils in the manner indicated above leads tothe wrapped products being unsuitable for practical use.

Our earlier application referred to above relates to a packaging foilcomprising one or more flexible support foils, a top layer of a vinyl orvinylidene polymer and an adhesion promoter or primer between thesupporting foil and the top layer wherein the primer is a mixture of a.a polymer of a compound of the general formula HQC=C wherein Xrepresents chlorine or fluorine and A represents hydrogen or has thesame meaning as X, and

b. a compound selected from the group consisting of an isocyanate of theformula:

wherein R represents hydrocarbyl having from one to 18 carbon atoms;cyclohydrocarbyl having from five to 12 carbon atoms; single, multipleand fused ring aryl radicals having from six to 20 carbon atoms; Y Z Ywherein Z represents hydrocarbyl having from one to three carbon atomsand Y represents single, multiple and fused aryl and cyclohydrocarbylradicals having from five to 20 carbon stoms; and n is an integer of atleast 2 which corresponds to the valence of R; and a polyurethane of theformula:

free from substituents reactive with an isocyanate and having amolecular weight above 480.

Although the adhesion promoter disclosed in our prior applicationgreatly improves adhesion, it has now been found that, in accordancewith the present invention, an even stronger adhesion promoting effectcan be obtained when the primer is a mixture containing an additionalcomponent (c) which is a reaction product having terminal hydroxylgroups and derived from a linear polyester with terminal hydroxyl groupsand an organic diisocyanate. Reaction products of this kind arecommercially available. They are marketed, for example, byFarbenfabriken Bayer AG., of Leverkusen, Germany, under the RegisteredTrade Mark Desmocol.

The aforesaid polyester component is a reaction product of dicarboxylicacids with diols. The dicarboxylic acid component preferably comprisesan aliphatic dicarboxylic acid with up to 10, and especially with fromfour to six, carbon atoms, for example, adipic acid. The diol componentpreferably comprises an aliphatic diol with from two to six carbonatoms.

The aforesaid diisocyanate component can be any conventionally employeddiisocyanate, for example, hexamethylenel, 6-diisocyanate (Desmodur H);tolylene-2, 4-diisocyanate (Desmodur T 2,4);naphthalene-l,5-diisocyanate (Desmodur 15); ordiphenylmethane-4,4-diisocyanate (Desmodur 44). Tolylene diisocyanate isparticularly suitable for this purpose.

Accordingly, the present invention relates to a packaging foil whereinthe primer is a mixture of a. a polymer of a compound of the generalformula H2C=C CA in which X represents chlorine or fluorine and Arepresents hydrogen or has the same meaning as X,

b. a compound selected from the group consisting of an isocyanate of theformula:

(R-)-(N=C=O) represents hydrocarbyl having from one to wherein R whereinR is as above and G is a long chain polymeric radical free fromsubstituents reactive with an isocyanate and having a molecular weightabove 480, and

c. a reaction product having terminal hydroxyl groups and derived from alinear polyester with terminal hydroxyl groups and an organicdiisocyanate, component (c) being present in such a quantity that thereare no more than 60 parts by weight of component (c) to 40 parts byweight of component (a).

Illustrative of compounds of the formulae for organic compound (b) are:Hexamethylene-l 6-diisocyanate, (Desmodur H), Toluene-2,4-diisocyanate,(Desmodur T 2,4; Mondur TDS; Nacconate Naphthalene-1,S-diisocyanate,(Desmodur 15; Multrathane N 5) Diphenylmethane-4,4'-diisocyanate,(Multrathane M; Desmodur 44;

Nacconate 300) Triphenylmethane-4,4, 4-triisocyanate, (Desmodur R;Mondur TM) and Polyurethane, formed by reaction of a OH-group containingpolyester with a mixture of toluene- 2,4-diisocyanate and toluene-2,(J-diisocyanate, (Desmophen VL 100).

Component (c) must contain terminal hydroxyl groups. In its preparation,therefore, the linear polyesters and diisocyanates must be reacted insubstantially equivalent quantities, except that the linear polyesterwith tenninal hydroxyl groups is used in a slight excess, so that theend product contains tenninal hydroxyl groups. Component (c)advantageously has a molecular weight of from 50,000 to 150,000 andpreferably around 100,000.

As top layer with a vinyl polymer base, it is likewise advantageous touse a polymer of a compound of the general formula in which X and A havethe meanings given above. Polymers which are preferred are those ofcompounds of the above formula in which X represents chlorine and Arepresents chlorine or hydrogen. This also applies in respect of thecomponent (a) of the primer.

Such polymers are the aforementioned PVDC or the PVC. Dispersions orsolutions of these polymers are conventional commercial products whichare produced on a large industrial scale and are known, for example,under Trade Marks such as Saran (Dow Chemical Co.), Diofan (BadischeAnilin and Soda-Fabrik, Ludwigshafen), and Ixan (Solvay, Brussels). Someof these products are not pure homo-polymers, but the polymers containother monomers which can be copolymerised with the compounds of theabove formula and which are incorporated by polymerisation. Inaccordance with the present invention, by polymers of the generalformula HIC=C A there are also to be understood those polymers which, inaccordance with the prior art, contain minor quantities of comonomers.The quantity of these comonomers can be up to 25 percent of the totalweight. Examples of suitable comonomers include acrylates,acrylonitriles, methacrylates, methacrylonitriles, vinyl chloride,styrene, maleates, vinyl esters, allyl crotonates, butadiene and epoxycompounds.

Such copolymers can likewise be used as component (a) of the primer ofthe packaging foil according to the invention. The comonomer ispreferably so selected that copolymers are obtained which have animproved solubility with respect to PVDC. A technical disadvantage ofpure PVDC is that it is comparatively sparingly soluble in easilyaccessible solvents. The use is thus facilitated by using, in theforegoing sense, copolymers which show an improved solubility inconventional solvents, such as ethyl acetate, methyl ethyl ketone,acetone or mixtures of these solvents. The reason for this is that theprimer is applied in the form of a solution to the flexible support foilwhich is to be coated.

The component (a) of the primer of the packaging foil according to theinvention contains the copolymerised monomeric compounds, advantageouslyin a quantity of 1 to 50 percent by weight based on the total weight ofthe component (a). Especially preferred are those polymers in which thecopolymerised compounds are present in a quantity of to 30 percent byweight, based on the total weight of the component (a). Such polymersshow a good solubility in the aforementioned solvents and as aconsequence can be handled particularly easily technically.

The degree of polymerisation of the compounds of general formula I,i.e., the molecular weight of these polymers, has the usual values,i.e., it is possible to use polymers with molecular weights such asthose which are normal for the production of packaging foils of theaforementioned known type with a top layer having a PVDC and/or PVCbase.

The conventional commercial isocyanate compounds can be used ascomponent (b) according to the present invention, i.e., as organiccompounds with at least two isocyanate groups.

Diisocyanates are particularly preferred, more especially because theseare easily available and are cheap. Triisocyanates or polyisocyanateswith more than three isocyanate groups can, for example, also be used.

As already stated above, the component (b) is present in such quantitiesthat the N C 0 content of the mixture, related to the solid content ofthe primer mixture, amounts to at least 0.1 percent by weight. In thissense, the isocyanate content of a primer mixture containing 98.26 g. ofcomponent (a) and 1.74 g. of toluylene diisocyanate amounts to 0.84percent by weight, since the molecular weight of toluylene diisocyanateis 174 and the weight of the two isocyanate groups in the toluylenediisocyanate is 84. 1.74 g. of toluylene diisocyanate thus contains, inaccordance with this definiation, 0.84 g. of isocyanate groups.

A remarkable effect on the bond strength between the support foil andthe top layer is already obtained with the previously indicated lowerlimit of at least 0.1 by weight of isocyanate groups. A best possiblebonding strength, also under tropical storage conditions, is obtained ifthe content of isocyanate groups, based on the solids, amounts to 2 to 7percent by weight. With a higher proportion, the effect is generallyprogressively weaker. Proportions of isocyanate greater than 10 percentby weight are generally unsuitable. The best possible quantity by weightnaturally depends on the type, i.e., more especially upon the molecularweight and the number of isocyanate groups in the polyisocyanate, andalso on the type of the component (a).

According to the present invention, component (c) can be used in aquantity of at most 60 parts by weight to 40 parts by weight ofcomponent (a). In general, an appreciably better effect is obtained whenthe quantity of component (c) is from 20 to 50 parts by weight to to 50parts by weight of component (a). Particularly good results are obtainedwith a ratio of around 40 parts by weight of component (c) to around 60parts by weight of component (a).

It is advisable to adapt the quantity of component (b) to the particularquantity in which component c) is added. The quantity of component (b)should then be measured in such a way that the N= C= 0 content of themixture, based on the total weight of the solids content, i.e.,component (a)+(b)+(c), is at least 0.5 percent by weight and morepreferably from 1 to 5 percent by weight, and most preferably from 2 to3 percent by weight.

Naturally, the mixture of component (a) and component (b) cannot bestored, but has a limited pot-life. As a rule, it has a pot life of from2 to 50 hours, depending upon a variety of factors, especially theconcentration, the water content of the solvent, and atmospherichumidity. The presence of moisture accelerates the reaction betweencomponents (a) and (b) naturally, the reactivity of the individualreaction components also affects pot-life. Accordingly, to prepare thepackaging film according to the invention, reaction components (a) and(b) are mixed together at some suitable time before they are used.Accordingly, the primers or reaction components are separately deliveredto the manufacturers of the packaging film. Components (a) and (b) canbe stored for long periods before mixing.

If in accordance with a preferred embodiment of the invention, theadhesion promoter also contains component (c), this component can bemixed with component (a) some time before use, because the mixture ofcomponent (c) and component (a) is storable. The manufacturer of thepackaging film then adds component (b) at some stage before usecorresponding to the pot-life of the mixture.

The invention also provides a process for producing the packaging filmaccording to the invention, wherein a solution or dispersion of a primeris applied to a flexible support layer, the solvent or dispersion mediumof the primer is evaporated, and a solution or dispersion of a vinyl orvinylidene polymer is applied thereto as top layer and the solvent ordispersion medium of this top layer is evaporated, wherein the primer isa mixture of the aforesaid components (a), (b), and (c), com- EXAMPLE 1An unstretched polypropylene film having a thickness of around 50 p. isexposed to a corona discharge to make its surface especially tacky andthen coated with a primer solution of the following composition:

54 parts by weight of vinylidene chloride/acrylonitrile copolymer (lxanWN, a product of SOLVAY, Brussels) parts by weight of diphenylmethanediisocyanate (isocyanate content around 3 3 percent by weight) 36 partsby weight of a polyurethane readily soluble in ethyl acetate (Desmocoll400, a product of Farbenfabriken Bayer, Leverkusen, Germany) 750 partsby weight of methyl ethyl ketone (solvent) The solution is applied insuch a quantity that, following evaporation of the solvent, a quantityof 0.3 g. of solids per sq. meter has been applied. The solvent is bestevaporated at a temperature of around 40C. with air being blown into adrying tunnel. A polyvinylidene chloride dispersion is then applied tothe polypropylene film thus coated, and dried by intra-red radiationwith vigorous circulation of air. The quantity applied amounts to around5 g. of solids per sq. meter of film. The dispersion used is onemarketed commercially as Diofan 190 D by Badische Anilin und Soda Fabrik(BASE), Ludwigshafen, Germany. The aqueous dispersion has a solidscontent of around 55 percent by weight. The film obtained showsoutstanding permeability to water vapour and gases. After storage for 6days at 40 C./90 percent relative humidity, there are no signs of anydeterioration in adhesion.

EXAMPLE 2 A polyamide film with a weight per unit area of 50 g. per sq.meter is coated with a primer of the following composition:

56 parts by weight of the vinylidene chloride/acrylonitrile copolymerused in Example 1 6 parts by weight of tolylene diisocyanate (isocyanatecontent approximately 48 percent by weight) 38 parts by weight of apolyurethane readily soluble in ethyl acetate (Desmocoll 405, a productof Farbenfabriken Bayer, Leverkusen), and

750 parts of methyl ethyl ketone (solvent).

The primary layer dried following evaporation of the solvent as inExample I weighs about I g. per sq. meter. A polyvinylidene chloridedispersion, for example lxan WA 91, is then applied to the film surfacethus treated, followed by drying as in Example 1. The dispersion isapplied in a layer thickness of 3 p..

EXAMPLE 3 Samples of a biaxially stretched polypropylene film having athickness of ,u. are pretreated in known manner by a corona dischargeand then coated with the primers described in Examples l and 2. Thequantity in which the primers are applied is such that, followingcomplete evaporation of the solvent, a quantity of around 0.5 g. per sq.meter is applied. The solvent is evaporated and a polyvinylidenechloride dispersion is subsequently applied as described in Example 1.

As support foil for use in accordance with the present invention, it ispossible to use foils of those materials which are also already incommon use for the known packaging foils of the type hereinbeforementioned. Especially preferred are foils of polypropylene polyvinylchloride, cellulose hydrate and polyesters, advantageously polyethyleneterephthalate. In accordance with the present invention, however, foilswith a base of other synthetic plastics materials, and also paper foilsor metal foils, can also be used as support foils. The support foils canconsist of a single web or of several foils which are stuck to oneanother.

We claim:

1. In a packaging foil comprising a flexible support member, a top layerof vinylpolymer wherein the vinyl polymer is a compound of the formula XHaC=C wherein X represents chlorine or fluorine and A representshydrogen or X, and an adhesion promoter disposed therebetween, theimprovement comprising an adhesion promoter which is a mixture of a. apolymer of a compound of the general formula HaC=C A in which Xrepresents chlorine or fluorine and A represents hydrogen or X,

b. an organic composition of matter bearing at least 2 isocyanatemoieties, N C O, with the solids content of i =.C= ,tnq st ssbdnsatJsastQ-l? pe cent by weight based upon the total weight of themixture, and

c. a reaction product having terminal hydroxyl groups and derived from alinear polyester with terminal hydroxyl groups and an organicdiisocyanate, component (c) being present in such a quantity that thereare no more than 60 parts by weight of component (c) to 40 parts byweight of component (a).

2. A packaging foil as claimed in claim 1 wherein component (c) has amolecular weight of from 50,000 to 150,000.

3. A packaging foil as claimed in claim 1 wherein the quantity ofcomponent (c) is from 20 to 50 parts by weight, to from to 50 parts byweight of component (a).

4. A packaging foil as claimed in claim 1 wherein the -N C 0 content ofthe primer mixture is at least 0.5 percent by weight, based on totalsolids content (a)+(b)+(c).

5. A packaging foil as claimed in claim 4 wherein the -N C 0 content isfroml to 5 percent by weight.

6. A packaging foil as claimed in claim 5 wherein the N C 0 content isfrom 2 to 3 percent by weight.

7. A packaging foil as claimed in claim I wherein the linear polyesteris derived from an aliphatic dicarboxylic acid with up to 10 carbonatoms.

8. A packaging foil as claimed in claim 1 wherein the linear polyesteris derived from an aliphatic diol with from two to six carbon atoms.

9. A packaging foil as claimed in claim 1 wherein the diisocyanate isselected from the group consisting of hexamethylene-l, o-diisocyanate;tolylene-2, 4-diisocyanate; naphthalene-l, S-diisocyanate; anddiphenyl-methane-4,4'- diisocyanate.

10. The packaging foil as defined by claim 1, wherein the vinyl polymerof the top layer is a polymer selected from the group consisting ofpolyvinylidene chloride and polyvinyl chloride.

11. The packaging foil as defined by claim 1, wherein the top layer iscomprised of a copolymer of a compound of the formula:

wherein X represents chlorine or fluorine and A represents hydrogen orX, and a comonomer copolymerizable therewith.

12. The packaging foil as defined by claim 1, wherein the polymer ofcomponent (a) is selected from the group consisting of polyvinylidenechloride and polyvinyl chloride.

13. The packaging foil as defined by claim 1, wherein the polymer ofcomponent (a) is a copolymer of a compound of the formula: X

wherein X represents chlorine or fluorine and A represents hydrogen orX, and a comonomer copolymerizable therewith.

14. The packaging foil as defined by claim 13, wherein the copolymer iscomprised of from between 1 and 50 percent by weight of thecopolymerizable comonomer.

15. The packaging foil as defined by claim 14, wherein thecopolymerizable comonomer. is an acrylate, a methacrylate,acrylonitrile, methacrylonitrile, styrene, a maleate, ally] crotonate, avinyl ester, butadiene, vinyl chloride an epoxide or mixtures thereof.

16. The packaging foil as defined by claim 1, wherein the flexiblesupport member is polypropylene, polyethylene, a polyester, a polyamide,polyvinyl chloride, paper, metal or cellulose hydrate.

17. The packaging foil as defined by claim 1, wherein the vinyl polymerof the top layer and adhesion promoter is polyvinylidene chloride.

18. A process for the production of a packaging foil which comprisesapplying a solution or dispersion of a primer to a flexible supportmember, evaporating the solvent or dispersion medium of the primer,applying a solution or dispersion of a vinyl or vinylidene polymerthereto as top layer and evaporating the solvent or dispersion medium ofthis top layer, wherein the primer is a mixture of a. a polymer of acompound of the general formula HnC=C it A i in which X representschlorine or fluorine and A represents hydrogen or has the same meaningas X,

b. an organic compound with at least 2 isocyanate, -N

C 0, groups. the N C 0 content, based on solids content (a)+(b), beingat least 0.1 percent by weight, which mixture additionally contains c. areaction product having terminal hydroxyl groups and derived from alinear polyester with terminal hydroxyl groups and an organicdiisocyanate, component (c) being present in such a quantity that thereare not more than 60 parts by weight of component (c) to 40 parts byweight of component (a).

2. A packaging foil as claimed in claim 1 wherein component (c) has amolecular weight of from 50,000 to 150,000.
 3. A packaging foil asclaimed in claim 1 wherein the quantity of component (c) is from 20 to50 parts by weight, to from 80 to 50 parts by weight of component (a).4. A packaging foil as claimed in claim 1 wherein the -N =C =O contentof the primer mixture is at least 0.5 percent by weight, based on totalsolids content (a)+(b)+(c).
 5. A packaging foil as claimed in claim 4wherein the -N =C =O content is from 1 to 5 percent by weight.
 6. Apackaging foil as claimed in claim 5 wherein the -N =C =O content isfrom 2 to 3 percent by weight.
 7. A packaging foil as claimed in claim 1wherein the linear polyester is derived from an aliphatic dicarboxylicacid with up to 10 carbon atoms.
 8. A packaging foil as claimed in claim1 wherein the linear polyester is derived from an aliphatic diol withfrom two to six carbon atoms.
 9. A packaging foil as claimed in claim 1wherein the diisocyanate is selected from the group consisting ofhexamethylene-1, 6-diisocyanate; tolylene-2, 4-diisocyanate;naphthalene-1, 5-diisocyanate; and diphenyl-methane-4,4''-diisocyanate.10. The packaging foil as defined by claim 1, wherein the vinyl polymerof the top layer is a polymer selected from the group consisting ofpolyvinylidene chloride and polyvinyl chloride.
 11. The packaging foilas defined by claim 1, wherein the top layer is comprised of a copolymerof a compound of the formula: wherein X represents chlorine or fluorineand A represents hydrogen or X, and a comonomer copolymerizabletherewith.
 12. The packaging foil as defined by claim 1, wherein thepolymer of component (a) is selected from the group consisting ofpolyvinylidene chloride and polyvinyl chloride.
 13. The packaging foilas defined by claim 1, wherein the polymer of component (a) is acopolymer of a compound of the formula: wherein X represents chlOrine orfluorine and A represents hydrogen or X, and a comonomer copolymerizabletherewith.
 14. The packaging foil as defined by claim 13, wherein thecopolymer is comprised of from between 1 and 50 percent by weight of thecopolymerizable comonomer.
 15. The packaging foil as defined by claim14, wherein the copolymerizable comonomer is an acrylate, amethacrylate, acrylonitrile, methacrylonitrile, styrene, a maleate,allyl crotonate, a vinyl ester, butadiene, vinyl chloride, an epoxide ormixtures thereof.
 16. The packaging foil as defined by claim 1, whereinthe flexible support member is polypropylene, polyethylene, a polyester,a polyamide, polyvinyl chloride, paper, metal or cellulose hydrate. 17.The packaging foil as defined by claim 1, wherein the vinyl polymer ofthe top layer and adhesion promoter is polyvinylidene chloride.
 18. Aprocess for the production of a packaging foil which comprises applyinga solution or dispersion of a primer to a flexible support member,evaporating the solvent or dispersion medium of the primer, applying asolution or dispersion of a vinyl or vinylidene polymer thereto as toplayer and evaporating the solvent or dispersion medium of this toplayer, wherein the primer is a mixture of a. a polymer of a compound ofthe general formula in which X represents chlorine or fluorine and Arepresents hydrogen or has the same meaning as X, b. an organic compoundwith at least 2 isocyanate, -N =C =O, groups, the -N =C =O content,based on solids content (a)+(b), being at least 0.1 percent by weight,which mixture additionally contains c. a reaction product havingterminal hydroxyl groups and derived from a linear polyester withterminal hydroxyl groups and an organic diisocyanate, component (c)being present in such a quantity that there are no more than 60 parts byweight of component (c) to 40 parts by weight of component (a).